energy is never used up. instead its just
transferred between different energy
stores and different objects
energy is transferred between stores.
thermal
kinetic
gravitational potential
elastic potential
chemical
magnetic
nucleur
when a system (a single object)
changes, energy is transferred
energy can be transferred
by heating
or doing work......
work done is just another way of
saying energy transferred
work can be done when current flows (work is done against
resistance in a circuit) or by a force moving an object.
kinetic and potential energy stores
movement means energy in an objects kinetic energy store
anything thats moving has energy in its kinetic energy store
energy is transferred TO this store when an object speeds
up and is transferred AWAY from this store when am object slows down
Ek = 1/2 x m x v squared
raised objects store energy in gravitational potential energy stores
lifting an object in a gravitational field requires work. this
causes transfer of energy to the gravitational potential enerygy
Ep (gpe) = mgh
falling objects also transfer energy
when something falls energy from its gravitational potential energy store is
transferred to its kinetic energy store
for a falling object when there is no air resistance......
energy lost from the gpe store = energy gained in the kinetic energy store
stretching or squashing an object can transfer energy to
its elastic potential energy store
Ee = 1/2 x k x e squared
SHC
heres the equation that links energy transferred
to specific heat capacity......
change in E = M x C (shc) x temp change
conservation of energy and power
energy is NEVER destroyed
energy can be transferred usefully, stored or
dissipated , but can never be destroyed.
when energy is transferred between stores, not all of the
energy is transferred usefully into the store that you want
it to go in
dissipated energy is sometimes called 'wasted energy'
because the energy is being stored in a way that is not
useful
conduction and convection
when an object is heated , energy is transferred to the kinetic energy stores of its particles.
this causes the particles to vibrate more and to collide with each other. during these collisions, energy is
transferred between the particles kinetic energy stores. this is conduction.
because liquids and gases can flow, the warmer and less dense region will rise above denser, cooler regions. so
energetic particles move away from hotter to cooler regions. this is convection.
insulation
thick walls
made from a material with a low thermal conductivity.
cavity walls
draught excluders
double glazed windows
efficiency
useful output energy transfer
// total input energy transfer